This invention relates generally to identification documents and a method for making such identification documents. More particularly, this invention relates to a secure identification document that allows detecting a fraudulent modification of the existing personalization or a completely falsified document. The invention also relates to a method for making such a document.
Identification documents, such as driving licenses, identity cards, membership cards, badges or passes, passports, discount cards, banking cards, money cards, multi-application cards, and other papers of value; and security documents such as bank notes are widely used. Because of the value and importance associated with each of these data carriers, they are often the subject of unauthorized copying and alterations, and forgeries.
To prevent such activities from being carried out on these data carriers, different types of visual and touchable security features have been added to data carriers. One of these security features consists in providing, into the document, an optically variable security element, which comprises at least two security markings. Said markings are decomposed and interleaved, so as to create a complex image that is printed into the document. Then, a filter is placed over this complex image, said filter being arranged so that it enables to visualize each marking at a respective particular angle by tilting the document.
Another security feature consists in providing a personalized image that is perforated through a document, but not extending through the whole thickness of the document. For that, blind holes are perforated, and the desired brightness tones are obtained by varying the density and/or the diameter and/or the depth of these holes. This technology is for example described in the document EP0936975.
Still another security feature consists in applying specific inks, such as UV inks, or IR inks for instance, onto the top surface of the data carrier, so that a security pattern can be revealed under predetermined lightening conditions. However, because they are applied onto the external surface of the document, such inks suffer from the environmental stresses. Therefore, the use of such inks onto the surface of identification documents is not compliant with a long-term life, which is required for identification documents that are usually delivered for ten years. On the other hand, some of these inks, namely short-wavelength UV inks, are generally absorbed, more or less, by plastic layers, depending on their thickness. That's the reason why such inks are not used inside identification document, because they cannot be sufficiently seen through the plastic constitution layers, whatever they are transparent or opaque.
Considering the above, a problem intended to be solved by the invention is to improve the existing solutions, and to find alternative solution to existing security features for identification documents comprising at least two constitution layers. Said identification document is personalized with personalization data and is secured with a security pattern, which forms the security feature. The problem is to use any inks to make the security pattern, said inks being able to be revealed under predetermined specific conditions, said inks being applied inside the constitution layers and no more onto the external surface of a document, in order to protect them against environmental stresses, and able to be selectively revealed in spite of the layers placed above that may either hidden or greatly soften their appearance.
Another problem intended to be solved by the invention is to provide a method for manufacturing a secure identification document comprising at least two constitution layers, said document being personalized with personalization data and being secured with a security pattern, said method being easy, quick to implement, and of low cost.